O-quinones



United States Patent O-QUINONES Albert L. Rocklin, Walnut Creek, Califl, assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application May 26, 1958 Serial No. 737,516

Claims. (Cl. 260-396) I l X X wherein each X represents an independently selected halogen having an atomic number from 17 to 35; i.e., chlorine or bromine.

In the practice of the invention, the halophenol is treated with nitric acid at a temperature of about 20 to 120 C. and preferably about 0 to 100, in the presence of an organic solvent which is a saturated aliphatic or aromatic hydrocarbon or a fiuoro, chloro, bromo or nitro derivative thereof. By the term solvent I mean a material that is in the liquid state under both normal (i.e., atmospheric pressure) and reaction conditions and that dissolves a significant amount of the halophenol and nitric acid or the equivalent nitric oxides.

The concentration of the nitric acid used is not important. Dilute aqueous acid is suitable, as is the common commercial concentratedacid of 68 percent concentration and also the pure (IOOpercent) acid. Moreover, fuming acid is entirely suitable, as is the equivalent anhydride, N 0 Thus, the required nitric acid may be formed in situ by supplying the required nitrogen oxide, oxygen and water. The amount of nitric acid used should be substantially in excess of that theoretically required in order to achieve high conversion and high reaction rates.

When the reaction is conducted at a temperature below -20 C., the rate of'reaction is needlessly low, thus making necessary a long reaction time in order to achieve a reasonably high conversion. On the other hand, at temperatures above about 120? C., the nitric acid may attack the product and thusdiminish the yield of the latter.

Suitable solvents include the saturated aliphatic hydrocarbons, aromatic hydrocarbons and flu-oro, chloro, bromo and nitro hydrocarbons. The structure, molecular weight, boiling point and other physical characteristics of the solvent are relatively unimportant insofar as operability is concerned, so long as the solvent is a liquid at the temperature and pressure at which the process is operated and dissolves a significant amount of the reactants. It is not necessary that the solvent dissolve all the reactants present. So long as a significant amount is dissolved, the part that is dissolved can readily react and then is replaced by an additional amount which dissolves. It is not necessary that the solvent dissolve the o benzoquinone produced in the process, though most of the operable solvents do so. This is advantageous, however, since it facilitates recovery or use of the product. As a practical matter, it is preferred that the solvent be a liquid under normal conditions (i.e., atmospheric pressure) and have a boiling point not higher than about 200 0., thus facilitating its handling and recovery.

Pressure is of no critical significance in the process. When a highly volatile solvent, such as methyl chloride or methylene chloride, is to be used at a temperature above its normal boiling point, it is necessary to use a closed system at superatmospheric pressure. On the other hand, when a relatively high-boiling solvent is to be used at a temperature below its normal boiling point, it may be convenient, though not necessary, to operate at a reduced pressure such that the solvent refluxes at the reaction temperature.

In making o-quinones by the process of the invention, the appropriate phenol is dissolved or suspended in a suitable solvent and the temperature is maintained at the chosen point in the range of about --20 to 120 C. while nitric acid is added with stirring. The reaction usually is rapid and is usually complete within a few minutes to, at most, a few hours after the reagents are mixed. The product is soluble in most solvents. If it is not soluble in the solvent being used, it can be recovered by merely filtering it from the reaction medium. If it is soluble, the solution containing the product can be sep arated from residual nitric acid by the addition of a large volume of water. The organic layer can then be separated and the solvent evaporated.

The practice of the invention is illustrated by the following typical examples:

EXAMPLE l.--o-CHLORANIL One hundred grams of pentachlorophenol were suspended in 200 ml. of methylene chloride. The solution was heated to the boiling point (41 C.) and vigorously stirred as 40 ml. of concentrated (68 percent) nitric acid was added over a period of two minutes. Stirring was continued for 15 minutes, after which the solution was cooled to 20 and ml. of water was carefully added. Air was then blown through the mixture to remove oxides of nitrogen, after which the organic layer was separated, washed with water, cooled to 10, and filtered. The solvent was then evaporated to produce 72 grams of crude o-chloranil. The product was purified by being dissolved in hot carbon tetrachloride (3 ml. per gram) and the resulting solution slowly cooled to 25. The purified ochloranil (55 grams) crystallized, leaving the impurities in solution.

By use of procedures generally similar to those described above, other experiments were carried out to show the efiect of varying the solvent, temperature, time, acid concentration and ratios of reagents, the results of some typical ones being shown in Table I. The conversion figure in the table in the percentage of the pentachlorophenol used that was converted to o-chloranil.

Table I PREPARATION OF o-CHLORANIL Nitric Acid Reaction Gondio-Chloranil Pentations Produced Ex. chloro- No. Solvent, m1. phenol,

Amt, Grams Temp., Time, Gonver- Yleld, Cone. m1. 0. Min. sion, Percent Percent 2 Methylene Chloride 50 Fuming 5 10 O 120 .d d 17. 5 100 36 15 40 100 36 15 2O 5O 20 60 20 50 2O 30 10 5 40 30 4O 5 40 420 do 5 5 240 Ohloroforrn 6 30 30 Carbon Tetraehloride 5 5 45 15 Isooctane 100 5 5 100 5 N itromethane 100 10 5 30 70 EXAMPLE 14.-o-BROMANIL Twenty grams of pentabromophenol, 6.5 ml. of concentrated nitric acid and 50 ml. of methylene chloride were mixed and held at 36 C. for 25 minutes while being continuously stirred. The mixture was then cooled and diluted with a large volume of water. Air was blown through the mixture to remove oxides of nitrogen, after which the organic layer was separated. The crude product was then left as a residue by evaporation of the solvent. Infrared analysis showed that o-bromanil was obtained in a yield of 60 percent.

EXAMPLE .3 -CHLORO-4,5, 6-TRIBROMO- BENZOQUINONE Fifteen grams of 2-chloro-3,4,5,6-tetrabromophenol, 5 ml. of concentrated nitric acid and 30 ml. of methylene chloride were stirred together at 38 C. for 12 minutes. The product was then isolated and analyzed as described in Example 14 and found to consist of a 60 percent yield of a mixture of o-bromanil and 3-chloro-4,5,6-tribromobenzoquinone.

EXAMPLE 16.-3-BROMO-4,5,6-TRICHLORO- BENZOQUINONE A 30 percent solution of 2,6-dibromo-3,4,5-trichlorophenol is oxidized with nitric acid substantially as described in Examples 14 and 15, thus producing 3-bromo- 4,5,6-trichlorobenzoquinone.

Results substantially similar to those shown in the above examples are obtained when the solvents there shown are replaced with other saturated aliphatic hydrocarbons such as pentane, hexane, cyclohexane, petroleum ether, kerosene, and the like; aromatic hydrocarbons such as benzene, toluene, xylene, cumene, cymene, amylbenzene and similar alkylbenzenes; halogenated hydrocarbons such as trifluorotrichloroethane, fluorobenzene, ethyl chloride, ethylene chloride, methyl chloroform, tetrachloroethylene, chlorinated pentanes, chlorobenzene, dior trichlorobenzene, chlorotolu ene, nuclearly chlorinated xylenes, ethylene bromide, 1,5-dibromopentane, dibromobenzene, bromochlorobenzene; or with a nitrohydrocarbon such as nitrobenzene, dinitrobenzene, nitrotoluene, obromonitrobenzene, chloronitroethane, and the like, or with a mixture of any such solvents.

This application is a continuation-in-part of mycopending application, Serial No. 648,774, filed March 27, 1957, now abandoned.

I claim:

1. A process for producing an o-benzoquinone having the formula wherein each X represents an independently selected halogen having an atomic number from 17 to 35, said process comprising the oxidation of a phenol having the formula wherein X is as defined above, by contacting with nitric acid a solution of said phenol in a solvent selected from the group consisting of alkanes, nitroalkanes, haloalkanes, halonitroalkanes, benzene, alkylbenzenes, halobenzenes, nitrobenzenes, alkylhalobenzenes, alkylnitrobenzes, halonitrobenzenes, alkylhalonitrobenzenes, and mixtures thereof, said solvent being liquid under normal conditions and under the reaction conditions of the process and having a normal boiling point not substantially in excess of about 200 C., said oxidation being conducted at a temperature of about 20 to C.

2. A process as defined in claim 1 wherein the solvent is a halogenated aliphatic hydrocarbon.

3. A process as defined in claim 2 wherein the halogen is chlorine.

4. A process as defined in claim 2 wherein the solvent is methylene chloride.

5. A process as defined in claim 1 wherein the temperature is about 0100 C.

References Cited in the file of this patent Kohn: Montashefte fiir Chemie, vol. 47, pp. 214, 230 and 236 (1926).

Brook: J. of the Chemical Society (London) (1952), pp. 5040-41.

Merz et al.: Berichte Deutsche Chemische Gesellschaft, vol. 5 p. 460 (1872).

Royals: Advanced Organic Chemistry, p. 504, Prentice Hall Inc., second printing, January 1956, copyright 1954. 

1. A PROCESS FOR PRODUCING AN O-BENZOQUINONE HAVING THE FORMULA 